Various forms of cores for use in investment casting have been proposed in the prior art. Generally speaking in the investment cores comprise an organic vehicle such as a wax which can be extruded, pressed or injected into various shapes using mold dies. The organic vehicle further includes dispersed therein refractory compounds as well as binders. Once the composition is molded into a desired shape for the eventual cast, the same is fired and cured. The subsequently fired core is then used in the investment casting process to hollow out a particular casting cavity.
The core composition is removed by various means such as water blasting chemical means via acid solution, as well as by autoclaving. The prior art has indicated various solutions to dissolve cores, typical of which is evinced in U.S. Pat. No. 4,922,991. This reference teaches a composite core which includes a water soluble aggregation and an insoluble binder. The aggregation comprises sucrose articles and the binder a phenolic resin. This reference does not teach an acid soluble binder and further is deficient in terms of providing a high percentage core composition incorporating a nitride silicone compound or an aluminum nitride compound.
U.S. Pat. No. 4,925,492, sets forth a ceramic core composition in which the mix for the core includes sodium chloride, fused silica, zircon and temporary binders to facilitate moldability of the mix. Similar to the '991 reference, this document does not teach a mix having a high percentage of binder material to thereby permit rapid removal of the core from the casting subsequent to the firing procedure. In addition, the same does not provide an acid soluble binder.
U.S. Pat. No. 4,530,722, relates to a binder based refractory composition for use in various casting procedures. This reference is primarily directed to a binder and not specifically to a core composition. Accordingly, the reference does not contemplate nor teach a core mix having a high content of binder material.